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Answer: Bridging of logos can be avoided at the punch logo design stage by paying attention to the angles of cut width and finer points of design. When ordering such tooling, it is imperative to inform the tooling manufacturer that the tablets will be film-coated. Reputable manufacturers have a great deal of experience to offer in this direction and should always be consulted prior to purchase.
Answer: The fundamental point here is that the tablet core should be designed with film coating in prospect. Marginal core quality in terms of capping incidence will never be improved by film coating; it will only serve to make such deficiencies more obvious.
It is difficult to be precise about the normally measured parameters such as diametral crushing strength (DCS) as, to a certain extent, the minimum quantitative values will depend on the coating equipment, its rotational speed, or the volume of fluidizing air.
As an example, a normal convex circular tablet 10 mm diameter should have a friability of less than 0.5% and a DCS of at least 100–120 N. Smaller diameter tablets can be allowed to have correspondingly lower DCSs.
Answer: In many ways, the circular biconvex tablet is an easy shape to film coat. A number of departures from this should be carefully assessed for their coating efficiency:
It should also be appreciated that the packing density of small tablets is going to be greater than for large tablets. This has the effect that a bed composed of relatively small tablets (and especially pellets) is more resistant to airflow than would occur with large tablets.
Read Also: Sugar Coating Defects, Causes, and Remedies
Answer: It must be appreciated that heat and mass transfer in a conventional pan is inherently poor, thus making such equipment a non-ideal choice, especially for aqueous processing. However, processing is possible under the following conditions. First, the cores should be robust as the process will be lengthy compared with that in a more appropriate piece of equipment. Especially in small pans (about 1 m diameter), there is a certain amount of equipment congestion; air spray gun(s), inlet air duct, and exhaust ducts have to be fitted into a small space. Spray ‘bounce’ tends to make the process messy but an option during solvent-based spraying (if permissible) is to utilize airless atomizing equipment.
Without drying air being able to be drawn completely through the tablet bed, debris from the coating will collect in the pan and may affect the final appearance of the tablets.
Read more on conventional coating pan
Answer: Regarding spray shape, this should be adjusted so that a wide, flattened cone of spray is obtained. However, if very smoothly coated tablets are desired regardless of other factors, then an unmodified cone could provide the required results.
With larger equipment, there is a general feeling that a gain in quality of coating will result if the spray is spread out between a number of guns, as opposed to being confined through one gun. This is practiced to counteract the fall-off in intensity of spray from the center point of the flattened cone to the edge.
As a guide, in a Manesty 120 Accelacota use four guns, and in a Model 360 use six guns. The use of a multiple gun set-up does impose the need to balance the liquid spray rate evenly between the guns. Overlap should be minimized as this will give rise to localized overwetting. Obviously, avoid spray reaching parts other than the tablet bed.
Answer: As a general rule in a side-vented pan, the spray should be aimed at the tablet cascade, about a third of the way down the tablet bed. Absolute gun-to-bed distances will be optimized by trial and error but the configuration suggested by the existing placement of fittings should be regarded as a satisfactory starting point.
It should be remembered, especially with large-scale equipment, that increasing the gun-to-bed distance will increase the tendency to spray drying and vice versa on decreasing the distance. This latter action will, of course, lead to a smoother coated surface utilizing the controlled tendency to overwet the tablet bed.
Answer: One should aim for a purpose-built pharmaceutical spray-gun. These have been made with GMP considerations in mind regarding materials of construction and ease of cleaning. They are generally easier to dismantle than spray-guns from other industries and do not require hand tools for this operation.
Answer: Peristaltic pumps give a finer control of liquid flow rate and permit easier stirring of the suspension. They are also, in general, smaller and more self-contained compared with pressurized vessels.
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